Add support for Rails generators

If anyone knows how to add tests for this, I'd love to add them. This stuff seems a bit under-documented in Rails, so  there were no examples of how to add tests.

I could write something that actually executes `rails generate pavlov:query` etc, but that seems incredibly slow...

In addition, I'd also love it if these generated the corresponding spec files, but rspec-rails doesn't provide generators for generic classes, only models, views etc. Might be an idea to add support for that to rspec-rails, so we can use it here. Ofcourse, then we'd also have to investigate how that works with Test::Unit and Minitest.